Saturday, May 16, 2009

Water Rocket Launcher Construction Tutorial: Part 8

Welcome Back, Water Rocket Enthusiasts!
In this installment of our Water Rocket launcher construction tutorial, we will begin the task of constructing a simple base for the launcher. There are many different materials we can use for the base and in this installment, we will be showing you how to make a basic wooden base for your launcher which closely resembles the now famous U.S. Water Rockets record setting L1 launcher.
To create this launcher, we will need to locate some wood and a few pieces of hardware. For our design, we chose to get some aspen planks from the local building supply box store. We chose aspen because it is low cost and reasonably hard. Plain pine can also be used, but we try to avoid it because it is a softer wood and therefore it can be more vulnerable to dings and scratches during use. Pine will be slightly less expensive, so the cost savings may be important, especially if you are building a large number of launchers for a scouting event.
Pictured below is the two aspen boards we purchased for this launcher. We purchased a 1/2"x3"x4' plank for the legs and an 1/2"x4"x3' plank for the body.
You can easily replace the aspen wood with some scrap building lumber if you wish, but you may have to compensate for different thickness lumber by using longer bolts or mounting hardware. If you wish, you can also substitute a hardwood like oak or maple in the design, which will be harder to work with but it will be much more resistant to damage while in use.
The next purchase needed for the launcher base is a pair of "U" Bolts which we will mount the PVC pipe launcher plumbing to the base with. We picked out a pair of U-bolts which are intended for use with 3/4" PVC pipe. The 3/4" pipe U-Bolts are just the right size to straddle the 1/2" PVC pipe fittings which we used on the launcher plumbing.
Tip: if you buy U-Bolts designed for 1/2" PVC pipe, they will only straddle the pipe itself and this will put the clamping force on the 1/2" PVC pipe which is somewhat flexible and will not hold as firmly as the rigid fittings. We recommend using the rigid fittings with the larger U-bolts to really clamp down the plumbing.
The first piece we will be making is the main body of the base. This piece will be the main structure which the other parts will attach. The length of the body must be created so that it is long enough to accommodate the legs of the launcher and still allow clearance for the mounting hardware. If you neglect to leave room for the hardware you will find yourself with a launcher you cannot assemble because the holes you made for the U-bolts are underneath the place the legs are attached.
The distance between the U-bolts is actually the same length as the PVC pipe at the bottom of the launcher plumbing. This length places the U-bolts right over the PVC fittings on either end of the pipe. In our case we have 8" for the distance. You can use any place on the fittings that places the U-bolts in a secure location and measure that distance to determine the U-bolt spacing. Make a note of the number.
We measured the width of our legs plus some extra spacing to allow for the nuts and mounting plate of the U-bolts. We simply set them in their rough positions and measured the space required. Since these dimensions are not critical, we rounded up to the nearest inch and came up with 3 inches of space required for each leg. We added the board length needed for 2 legs plus the length needed for the PVC tube which is 3"+3"+8", giving us 14" for our main body length. If this is too much detail work, you can just cut the legs to a reasonable size and then simply take the leg pieces and mock up the launcher in the final configuration and with the parts placed together like this you can make a mark on the main body board which will give a rough estimate of the correct length.
We marked out a 14" length of the 1/2"x4"x3' board for the main body of the base, and for our legs we used the 1/2"x3"x4' board. For the length of the legs, we picked an arbitrary length of 12". This length means one 4' board would yield four complete legs.
There is nothing special about the length of the legs. A rule of thumb would be to make sure it's not shorter than 50% of the main body length. This will insure the legs are wide enough to be stable.
Below, we mark out the 14" main body and 12" lengths of our leg boards and cut them.
Notice that we have used a small carpenter's square to insure that our lines are all at perfect 90 degree angles. We want to try and make our cuts as square as possible when we make them. This only serves to make the launcher look more professional and really isn't critical to the operation in any way. How hard you work on the cosmetics is entirely up to you. You may want to put the effort into making a neat cut now because we will be giving tips on how to customize and dress up the launcher in the future and a neat job here will pay off handsomely then.
We now have the two legs and the main body board cut and ready for more work. Bear in mind that these proportions and board sizes are not very critical, and we picked the dimensions we did for reasons of aesthetics as well as to try and optimize the number of launcher pieces we could make using standard board lengths found in our local store. Please feel free to tweak the sizes to whatever suits your needs.
Be sure and tune back in next week, where we begin the process of assembling the launcher base. The next steps will detail some nice shortcuts to getting a really professional and accurate looking final launcher.

Remember, the launcher is the one part of your water rocket arsenal which will usually be used for year after year. If you build it right, you will never have to replace it ever again. You will be able to spend your time building and flying rockets instead of constantly building new launchers. Look at the L1 launcher we use at U.S. Water Rockets... it's been in use since 2003! Most of it is unchanged since it was first used. We've made some upgrades and used steel pipe to hold more pressure, but it's the same launcher we first started with.

Another motivating point is that since this one piece of your equipment is going to be used for years and years, you should seriously consider making it as nice as you can because you're going to be using it for a long, long time.
See you next week!

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